A few weeks ago someone (Peter Rowe?) suggested using surplus
Space Shuttle heat shielding for a platinum soldering block.
Could someone please send me on where to buy this
material. I looked at the Boeing surplus store page, and even
sent a request to one of their sales people, but got no
response.

HI my name is john and I live in Seattle, I chanced across a box
of tiles quite some time ago, I don’t Know for sure but I think
If you called Dow-corning you might have some answers there, I
will look to see if I can find anymore next time I am
there. Ringman…Ps. check NASA

Unless they’ve changed, space shuttle heat shieldings proper
name is “kaowool”. Wonderful material which is actually, I
believe, spun kaolin. It comes in blankets of various thickness
as well as a fibreboard which is harder to find but more
durable. You should be able to locate these materials at a
refractory supply. I have a few local sources if you need them.

I would like to know about that resource also, the tile I got
were the first proto and were a type of ceramic, but were
changed in favor of a material that had fiber to prevent heat
breakage, I have been unable to find them again and people ask
me for them … Ringman

I use the 6X6" size and find them just right for benchtop and I
like the rubber feet they have as they lift the pad up off the
flammable benchtop to prevent scorching (just don’t heat the
corners as the rubber will melt! :0 I believe they’re great for
both silver, gold or platinum as they are very hard, heat
resistant, can be scrubbed clean as necessary and they wear like
iron.

Personally, Steve, I disagree with you about that line of
blocks, which is not exclusive to Gesswein, of course.

The block is highly sintered, which results in nice durable
surface hardness, but it also makes it more brittle, and prone to
heat shock. If they marketed it just for gold and silver, it
would probably be OK. but they market those things for platinum
use too, and at those temps, though the block takes the heat
without undue melting, it often cracks from uneven heating from
one part of the block to another. Plus, the high degree of
sintering makes the things very good heat conductors for a
ceramic. Wanna guess what that does to those rubber feet you so
like? My personal opinion of those rubber feet is not
completely printable. And I’d guess the engineer or whomever
decided to put them on is not someone who has ever seriously used
a torch with one of those blocks. You don’t need to be heating
the corner. with a six by six inch block, withing an hours worth
of platinum work in the center of the block, the rubber feet had
completely melted, making a ghod-awful mess of the bench, which
of course was also now starting to scorch nicely. If you take
off the rubber feet, and use a suitible solvent to clean off the
remaining glue, you can then use these blocks on a piece of
transite board underneath to protect the benchtop. THAT, at
least works. Until the block cracks that is. After I broke the
second one in thirds with a platinum soldering job within six
months of buying the first one, i’ve not gone back to these
blocks.

What I use now is a bit unusual. I’d really like to be using
the blocks made by wesgo, makers of the platinum melting dishes
and crucibles. Similar to your soldering blocks listed above,
but less highly sintered, and therefor slightly better insulated,
and a LOT less brittle and prone to cracking. (A much better
product, IMHO) but at something like forty bucks each, they’re
way too expensive for my poor blood, especially when I can
scrounge something just as good for almost free…

Until a couple years ago, I worked for a firm that did a good
deal of platinum casting. They’d upgraded to an induction melt
machine, and no longer had a use for the large box of mostly
cracked and flawed wesgo casting crucibles in the back. Those
crucibles don’t last forever before cracking here or there, but
the cracks are usually in the top “cover” part of the form, not
the base. So I set up a couple of those crucibles on a lapidary
slab saw and sliced off the bottoms. Left me with a pad slightly
thinner than the one wesgo sells actually as a pad, and it’s got
a slight hollow in one side. But other than that, it makes a
great little solder pad. I cut off several of them this way,
and I’ve yet to break or crack even one of em. I do use them on
a surface I won’t be burning, such as the solder pad that comes
on my benchmate soldering station.

Also, if you use these for platinum, DONT use them also for
gold. The reason is not the possible contamination of the
platinum by the gold. THAT is easy to avoid if you’ve got eyes
that work OK. The problem is that working with gold or silver,
we use varius fluxes. And those fluxes, as well as boric acid,
will get on the solder pad. When that is then heated to the
melting temp of platinum or platinum solders, those fluxes will
attack the solder pad a bit, changing the surface composition to
a mix of the flux componants and the solder pad componants. The
result is a glass that melts a fair bit lower than the pad
itself, and will then stick to your platinum if you let it.
But, it won’t come off nicely in the pickle. quite a pain in the
rear to then clean off. So if you work platinum, either with a
wesgo pad, crucible, or the above mentioned solder pads, reserve
a CLEAN one for use exclusively with platinum, and don’t get flux
or boric acid on that pad.

I appreciate your info. apperently gained through experience. I
primarily work in gold and only occasionally in plat. so I lack
long-term experience with it. Actually, I’m only just learning
about working with the noble metal. Of course, you’re absolutly
right about those %#@$*& rubber feet. I only had one melt on me
and it never returned to a solid state so I get it on my hand
everytime I lift the pad for cleaning. I think, however that I’ll
stick to the pads (bad pun) since I’m so heavily invested and
use one for gold & another for plat. as you suggest.

I think, however that I'll stick to the pads (bad pun) since
I'm so heavily invested :) and use one for gold & another for
plat. as you suggest.

Steve, regarding using two pads, one for gold, one for platinum,
here’s a sensible alternative. Don’t bother with one for
platinum. You’ll just burn your bench through those things. For
gold and silver, though, once the bloody feet are cleaned off,
they’re fine. Then get a wesco fused silica melting dish. Not
the high back one, the one that’s level all around. You can use
the dish half for whatever you like, but keep the bottom clean
and use it for platinum work. The fact that the underside of
your platinum work surface will be a hollow, up off the desk, and
the actual contact will be a far removed rim of the dish with
your bench, will mean you have no problems with the melting dish
burning your bench when used as a platinum soldering block…